GEOLOGICA BALCANICA, 42. 1 – 3, Sofia, Dec. 2013, p. 29-47. The Balkan Fold-Thrust Belt: an overview of the main features Dian Vangelov1, Yanko Gerdjikov1, Alexandre Kounov2, Anna Lazarova3 1Sofia University “St. Kliment Ohridski”, 15 Tsar Osvoboditel Blvd, 1504 Sofia, Bulgaria; e-mail:
[email protected] 2Geological-Paleontological Institute, Geoscience Department, Basel University; e-mail:
[email protected] 3Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria; e-mail:
[email protected] (Accepted in revised form: November 2013) Abstract. The Balkan Fold-Thrust Belt is a part of the northern branch of the Alpine-Himalayan orogen in the Balkan Peninsula and represents a Tertiary structure developed along the southern margin of the Moesian Platform. The thrust belt displays of two clearly distinct parts: an eastern one dominated exclusively by thin-skinned thrusting and a western part showing ubiquitous basement involvement. A wide transitional zone is locked between both parts where the structural style is dominantly thin-skinned, but with significant pre-Mesozoic basement involvement in the more internal parts. For the western thick-skinned part the poorly developed syn-orogenic flysch is a characteristic feature that along with the very restricted development of foreland basin suggests a rather limited orogenic shortening compared to the eastern part of the belt. The Tertiary Balkan Fold-Thrust Belt originated mainly through a basement- driven shortening and this is explained by the occurrence of compatibly oriented reactivated basement weak zones of pre-Carboniferous, Jurassic and Early Cretaceous ages. The proposed re-definition of the Balkan thrusts system and internal structure of the allochthons also call for significant re-assessment of the existing schemes of tectonic subdivision.